Video distribution systems have been suffering problems in that they fail to provide sufficiently guaranteed QoS (Quality of Service) and, as a result, cannot guarantee a bandwidth that is required for distributing video content and do not necessarily render services that operate stably.
The invention disclosed in Patent document 1 (JP-A No. 2003-051846) is directed to a technology for obtaining a bandwidth required for video distribution. Patent document 1 reveals a system wherein when a content request is received from a user terminal, a content server sends a bandwidth reservation request to a region manager, and, if the region manager is able to accept the bandwidth reservation request, the region manager sends a bandwidth reservation setting request to a bandwidth controller.
Patent document 2 (JP-A No. 2005-12655) has been proposed because the control between the content server and the region manager in the invention disclosed in Patent document 1 is complex and it has cost and flexibility problems that remain to be solved because general-purpose protocols are not applied.
According to the invention disclosed in Patent document 2, when a terminal requests a content distribution subsystem to establish a session, an SIP (Session Initiation Protocol) session control subsystem acquires information about a bandwidth needed for viewing content from the content distribution subsystem, and sends a bandwidth reservation request to a bandwidth control subsystem, and the content distribution subsystem transmits the content to the terminal in the bandwidth that is secured by the bandwidth control subsystem.    Patent document 1: JP-A No. 2003-051846    Patent document 2: JP-A No. 2005-12655